graham



(No Model.) 2 Sheets-Sheet 2. A. GRAHAM.

TELEPHONE SYSTEM.

Patented July 14, 1896;

UNITED STATES PATENT ALFRED GRAHAM, OF LONDON, ENGLAND.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters PatentNo. 563,920, dated July 14, 1896.

Application filed May 3, 1894. Serial No. 509,951. iNo modeld To all whom it may concern.:

Be it known that I, ALFRED GRAHAM, a

subject of the Queen oi' Great Britain, residing at London, England, have invented a certain new and useful Improvement in 'l`elephone Systems, oi' which the following is a specification.

The object I have in:view is a simple and effective arrangement of telephone-circuits, whereby loud-speaking apparatus can he cmployed, doing away with the necessity of callbells, itc.

My object further is to .provide a system of this character capable of connecting together a number oi'stations, so that there may lic interconnnunicaiion without thenecessity of an exchange or similar s\\"ite,hhoard, and at the same time givingthe advantages oi an exchange system with one telephone on each line, in the ability to establish connnunication between any two stations without disturbing the apparatus at other stations and without the possibility of the conversation being overheard at other stations. This l accomplish by placing the telephone-receiver of euch station in an independent circuit which extends to one or more other stations in the system, so that the transmitter at any Ystation maybe connected with anyone of the receivers without passing through the receiver of any other station. ln-ch receiver being ih an independent circuit, there will be connected with this circuit when in oper. tion only the transmitter and receiver and the battery to supply the current. vThis enables the effective employment of loudspeaking telephones, so that no call-bells are required.

In a system in which only two stations are employed there'will he an independent Wire for each receiver, and the transmitter at one station will he connected with the receiver at the other station through this wire.

In a system employing more than two sta.

tions the transmitter at each station will be connected with a switch-arm by means of which it can be connected to any one of the recevenwires of the system. The apparatus may also be provided at each of the two or more stations with a silent receiver which may he used in carrying on the conversation if it is not desired that it should he over heard by other persons in the same room.A This silent receiver maybe hung on a switcharm which will maintain the loud-speaking liig. i2 is a similar diagram showing the employinent of one battery to work all the lines. Fig. 23 is a view of the simplest form of the invention, illustrating two stations. Fig. #i shows the employment of the silent receiver. Referring to Fig. l, A, B, C, and D are four 1ine-wires with which are connected receiving-telephones c c d. These receivers are connected with the wires at the stations 1, il, J3, und l, to which all the wires run. A common return-wire E connects all the receivers together. At the four stations nre telephonetrnnsmitters e. 'lkhese are connected through normally open circuit-controllers fand hat tei-ics g to the common return-wire l). The other wire from cach transmitter is connected.

to aswingingswitcl1-a1m 7L., whose free end is adapted to he moved into connection with any one of three contacts. These contacts at each station are connected by wires with the three line-wires to which the receivers of the other stations are connected. The contacts at each station are numbered on the hoard on which they are mounted with the numbers of the other stations, as shown. Thus the transmitter at station 1 can he connected with the receivers of stations E?, 3, and i. The tra-nsmitter at station 2 can be connected with the receivers of stations l, 3, and l, and likewise with the other stations.

In Fig. 1 stations 2 and 4 are connected together and stations 1 and El may he considered as not in use. The operator at station 2 talks over the line A to the receiver at station i, while the operator at station i talks over the line C to the receiver at station 2. 1When the conversation is completed, the switches may he left as they were in use. lVhen one user desires to call up another, he throws his switch-arm 7a. onto the 'button hearing the number-of the other station. He then -a sound inthe receiver of the station being called. 4IIe then calls through his transmitter, giving his name or number, and the loudspeaking lreceiver may be heard by the person at the other station, who then moves his switch-arm'onto the contact for the station which is calling him, and the apparatus will be ready for the `commencement of conversation.

Since the receiver at a station is connected to its own independent wire and cannot be connected to any other receiver-wire, the conversation cannot be overheard.

In Fig. 2 the same arrangement is shown as in Fig. -l, except that in place of a sin gle return-wire E, two return-wires E F are employed, and a single battery G is placed between the two return-wires, which answers for all the stations.

. In Fig. 3 a simple system of two stations is shown. Two batteries are shown in the iigure, but a single battery placed in the common return may be employed. In the operation of the apparatus, each circuit will contain only a transmitter, receiver, and the operating-battery, and with transmitters and receivers adapted for the purpose loud talk ing can be secured.

In Fig. 4 the addition of the silent receiver is shown. This receiver shown atI I) is hung upon a switch-hook K, playing between two contacts 1'. 7c. ,Vhen the silent receivers are hung upon their hooks, the switch-arms will rest on the lower contacts' t', and the loudspeaking receivers will be in circuit; but when the silent receivers are removed from the hooks, the switch-arms will move to the up- 'per contacts 71;, opening the circuits through the loud-speaking receivers, and closing them through the silent receivers.

It is evident that the silent receivers may be used in systems having any number of stations, and it is also evident that my system is applicable to any number of stations for which it maybe found practicable to run independent wires.

The system is especially adapted for use in factories, houses, hotels,ofiices, rte. ,where it is desired to connect together a number of stations or in small towns where the expense oil a local exchange may be advantageously avoided.

Forms of a transmitter and receiver Well adapted for use with this system and capable of producing loud and clear articulation are described in applications for patents oi' even date herewith, Serial Nos. 509,959, 509,951, and 509,952, but since other instruments may be used, I do not wish to limit this invention to the particular yforms of instruments ilescribed in such applications.

'What I claim as my invention isl. In a telephone system having two or more stations, the combination of independent receiver-circuits, a talkin g-recciver at each station connected permanently with its partie ular receiver-circuit, a talking-transmitter at each station adapted to be connected in circuit with anyone of the receiver-circuits of the distant stations, and a returncircuit or ground connected between the transmitter yand receiver at each station, substantially as set forth.

2. In a telephone system having three or more stations, the combination of a separate line-wire for the receiver of'each station, extending to two or more other stations, and having a talking-receiver connected permanently therewith, with transmitters at the several stations, a switch at each station for connecting the transmitter of that station with the receiver-wire of any other station, and a return-circuit or ground connected between the transmitter and receiver at each station, substantially as set forth.

3. In a telephone system having three or more stations, the combination of a separate line-wire for the receiver of each station, extending to the two or more other stations, and having the talking-receiver connected permanently therewith, with transmitters at the several stations, a switch at each station for 4connecting the t-ransrnitter of that station with the receiver-wire of any oi' the other stations, a normally open circuit-closer in the transmitter-circuit at each station, and a rc turn-circuit or ground connected between the transmitter and receiver at each station, substantially as set forth.

et. In atelephone system having two or more i stations, the combination of independent receiver-circuits, a talking-receiver at each station connected permanently with its particular receiver-circuit, a talking-transmitter at each station adapted to be connected in circuit with any of the receiver-circuits of the distant stations, a wire common to the talking-receivers, a wire common to the talkingtransmitters, and a battery connecting said wi res, substantially as set forth.

5. In a telephone system having two-or more stations, the combination with independent receiver-wires and loud-talkin g receivers connected with such wires, of silent receivers at such stations and a switch at each station for substituting the silent receiver for the loudtalking receiver`l in the circuit, substantially as set forth.

This specifi cationsigned and witnessed this '25th day of April, 1894.

. ALFRED GRAHAM. Witnesses:

EUGENE CONRAN,

W. PELZER. 

